When Nick is stealing the BMW, his father kicks the window with his foot leaving two footprints on it. After a couple of scenes the marks have moved upwards from their first location.
The word 'acquaintance' is spelled incorrectly on the lower 3rd when Trent is being interviewed on TV
Two similar E46 BMW 3 series vehicles are clearly visible: first a 1999-2001 and after 2002-2005. You can notice the two similar vehicles with Nick Twisp (Michael Cera) faking his death.
In the scene where Nick is writing a letter to Bernice, he writes right to left, not left to right, and he positions his hand in a way very common to left-handed people (with his wrist above the writing, so as not to smudge what he's already written with his hand).